The Swiss Mammography Screening Pilot Programme was conducted between 1993 and 1998 in three areas of the French-speaking canton of Vaud. Socio-demographic characteristics were available for the whole of the target population and were used to identify determinants of initial (in the first round) and repeated (in both first and second rounds) non-attendance by means of logistic regression analyses. Initial non-attendance was higher among non-Swiss, single or divorced/separated women, and increased with distance between the residence and the screening centre. Being single and aged 65-70, not living in the vicinity of the screening centre and replying to decline the invitation to the initial screening session significantly increased the odds of persisting in non-attendance for screening within the programme. Factors such as age, nationality, marital status and screening centre differed in their influence on initial and repeated non-attendance, and the type of reply to the invitation was strongly predictive of non-attendance in the next round.